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ABSTRACT Title of Document: HOW MANY MINDS? INDIVIDUATING MENTAL TOKENS in the SPLIT-BRAIN SUBJECT Elizabeth Schechter, Ph.D., 2

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ABSTRACT Title of Document: HOW MANY MINDS? INDIVIDUATING MENTAL TOKENS in the SPLIT-BRAIN SUBJECT Elizabeth Schechter, Ph.D., 2 ABSTRACT Title of Document: HOW MANY MINDS? INDIVIDUATING MENTAL TOKENS IN THE SPLIT-BRAIN SUBJECT Elizabeth Schechter, Ph.D., 2009 Directed By: Professor Peter Carruthers, Department of Philosophy The “split-brain” cases raise numerous difficult and fascinating questions: questions about our own self-knowledge, about the limits of introspection and phenomenology, about personal identity, and about the nature of consciousness and of mind. While the phenomenon is therefore of relevance to many areas of psychological inquiry, my dissertation explores the split-brain studies from the perspective of theoretical psychology. The dissertation uses the split-brain cases to develop criteria for individuating mental tokens, and then applies those criteria back to the split-brain subjects themselves, ultimately arguing that split-brain subjects have two minds and two streams of consciousness apiece. Because the dissertation defends a particular account of the constitutive conditions for mental tokens against competing functionalist accounts, it also ends up being about the proper form for functionalist theories of the mental to take. I argue throughout that psychofunctionalists who are realists about mental phenomena should accept that the constitutive conditions for mental tokens are partly neural. In particular I argue that, within an organism, multiple neural events that sustain mental phenomena causally independently of each other in some relevant sense cannot be identified with a unique mental token, regardless of how unified that organism’s behavior may seem. HOW MANY MINDS? INDIVIDUATING MENTAL TOKENS IN THE SPLIT-BRAIN SUBJECT By Elizabeth Schechter Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park, in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2009 Advisory Committee: Professor Peter Carruthers, Chair Professor Georges Rey Distinguished University Professor Jerrold Levinson Associate Professor Allen Stairs Distinguished University Professor Emeritus William Hodos © Copyright by Elizabeth Schechter 2009 Acknowledgements Thanks to my family, for providing every kind of life support, year after year. And for the grammatical advice! Many thanks to friends who consented to read parts of this dissertation at one point or another (i.e. Ryan Millsap, Matt King, Brendan Ritchie, Mark Engelbert, and Bénédicte Veillet). Thank you, Mark, for the reassuringly bored certainty that the disaster-tation was anything but. Thank you, Bénédicte, for sharing all the sage wisdom—and for leading the way! Thanks most of all to members of my committee: to Allen Stairs, for helping me balance the demands of teaching and writing, to Bill Hodos, for the patient, outside perspective, and for general calm, experience, and good humor, to Jerry Levinson, for several kind pep-talks over the years—every time I most needed one, like magic, to Georges Rey, for early enthusiasm, for continued inspiration, and for helping me see the big picture (even in my own work), and especially to Peter Carruthers, who deserves more of my gratitude than I can ever express without embarrassing both of us. ii Table of Contents Acknowledgements ....................................................................................................... ii Table of Contents ......................................................................................................... iii List of Figures ............................................................................................................... v Chapter 1: Introduction ................................................................................................. 1 1 A History of the “Split” Brain .......................................................................... 1 2 Minds, Brains, and Unity .................................................................................. 8 2.1 Brain Bisection and the Unity of Consciousness .................................... 10 2.2 Five Hypotheses ...................................................................................... 13 3 Conclusion ...................................................................................................... 24 Chapter 2: On Individuating Minds and Other Mental Entities .................................. 27 1 Introduction ..................................................................................................... 27 2 On Mental Entities .......................................................................................... 29 2.1 Types, Tokens, States, and Systems ....................................................... 30 2.2 Identity and Individuation ....................................................................... 34 2.3 On Kinds of Questions ............................................................................ 44 3 The Criteria for Mindedness ........................................................................... 48 3.1 Modest Criteria for Mindhood ................................................................ 48 3.2 Purely Psychological versus Partly Neural Criteria for Mindhood ........ 51 4 Individuating Minds ........................................................................................ 63 4.1 Inter- versus Intra-mind Interactions ...................................................... 63 4.2 Deliberate versus Non-deliberate Interactions ........................................ 66 4.3 Direct versus Indirect Interactions between Mental States ..................... 69 5 Conclusion ...................................................................................................... 82 Chapter 3: A Defense of the Mental Duality Model ................................................... 84 1 Introduction ..................................................................................................... 84 2 Isomorphism and the Relationship between Neural and Psychological Facts 87 3 Behavior and Psychological Explanation ..................................................... 103 4 Perfect Parallelism: Does Redundancy Matter? ........................................... 121 4.1 STR: Meaning, Motivation, and Empirical Adequacy ......................... 123 4.2 Constituting a Single Token.................................................................. 127 4.3 Three Claims on Irrelevance ................................................................. 132 4.4 Mental Tokens ...................................................................................... 145 5 On Integrating Theory and Practice .............................................................. 153 5.1 Entities and Evidence ............................................................................ 154 5.2 Minds and Persons ................................................................................ 162 6 Duality versus Partial Co-mentality .............................................................. 173 6.1 Partial Co-Mentality (Or, an Indeterminate Number of Minds?) ......... 174 6.2 Subcortical Structures: Plausible Sources of (Interhemispheric) Mental Integration? ....................................................................................................... 179 6.3 What Kind of Interhemispheric Relations Do Non-cortical Structures Afford? .............................................................................................................. 191 7 Conclusion .................................................................................................... 208 iii Chapter 4: On Co-consciousness and Conscious Unity ............................................ 210 1 Introduction ................................................................................................... 210 2 Puccetti .......................................................................................................... 211 3 Some Claims and Distinctions ...................................................................... 216 3.1 Right Hemisphere Consciousness ......................................................... 216 3.2 Access versus Phenomenal Consciousness ........................................... 219 3.3 Co-consciousness .................................................................................. 222 3.4 A Unified Consciousness versus a Stream of Consciousness ............... 226 3.5 Consciousness and Subjects of Experience .......................................... 233 3.6 What is Co-consciousness? ................................................................... 237 3.7 Preliminary Conclusions and Assumptions .......................................... 244 4 The Conscious Duality Model and the Challenge from Unified Behavior ... 245 4.1 Duplication of Contents ........................................................................ 250 4.2 Attention ............................................................................................... 257 4.3 Cross-cuing ........................................................................................... 265 4.4 Affect… and Aura? ............................................................................... 267 4.5 Same Body ............................................................................................ 269 4.6 Same Brain ............................................................................................ 272 4.7 Single Hemisphere Control ................................................................... 273 4.8 Owing Actions .....................................................................................
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